PDCD1 and Miyoshi myopathy: Specifically, several critical immune checkpoints, such as PD‐1/PD‐L2, galectin‐9/T‐cell immunoglobulin mucin‐3 and ICOS/ICOSL, on both MM and immune effector cells and a number of activated PD‐1+ CD8 T cells lacking CD28 were distinguished in MM patients, and they serve as novel targets for developing more potent and efficacious checkpoint blockade‐based MM immunotherapeutic strategies.